title: The polar phase of Li2Ge4O9 at 298, 150 and 90 K.
abstract: Dilithium tetragermanate is orthorhombic, space group P2(1)ca, at 298 K, and is thus in a polar and probably a ferroelectric state. The structure contains two independent Li, four Ge and nine O atoms, all on general positions with site symmetry 1. Three tetrahedrally coordinated Ge positions form crumpled crankshaft-like chains, forming sheets within the ac plane, and these are interconnected by the fourth, octahedrally coordinated, Ge sites along the b direction. The GeO4 tetrahedra and GeO6 octahedra form a three-dimensional framework containing two different cavities, hosting the two 4+1-coordinated Li sites. Cooling to 90 K does not alter the space-group symmetry; the tetrahedral chains behave as a rigid unit and changes occur mainly within the Li coordination spheres.
authors.affiliation: Department of Materials Science and Physics, Division of Mineralogy, University of Salzburg, 5020 Salzburg, Austria.
authors.forename: Günther J
authors.initials: GJ
authors.lastname: Redhammer
authors.forename: Gerold
authors.initials: G
authors.lastname: Tippelt
keywords: crystal structure; lithium germanates